With the exception of identical twins, individuals have different genetic makeup, which results from two key processes. During meiosis, maternal and paternal homologous chromosomes assort randomly to form daughter cells (gametes), thus generating different combinations of maternal and paternal chromosomes. Additional variation is generated by recombinations or crossovers, in which parts of homologous chromosomes are exchanged, resulting in a new combination of parental alleles. Parvanov et al., Baudat et al., and Myers et al. report the identification of a mammalian geneâ€”PR domain containing 9 (PRDM9)â€”that controls the extent to which crossovers occur in preferred chromosomal locations, known as "hotspots."

Author and Copyright

Authors and Editors:Vivian Cheung of Departments of Pediatrics and Genetics, Howard Hughes Medical Institute, Stephanie Sherman of Department of Human Genetics, Emory University, Eleanor Feingold of University of PittsburghPublisher:AAASFormat:text/htmlCopyright and other restrictions:YesCost:No